SCOTTSDALE, Ariz. -- Three weeks remain before Opening Day on the mainland -- in other words, not the two regular season games in Australia.

So, 20 days between now and then, which is perhaps not enough time for right-handed pitcher Bronson Arroyo to be ready to open the season in the starting rotation.

"It's possible," manager Kirk Gibson said Tuesday.

Arroyo has been troubled by a stiff back. It first flared up just prior to what would have been his second start for the Diamondbacks on March 4. He was scratched from his scheduled start, and an MRI the next day revealed a bulging disk.

Arroyo, who received an epidural, played catch for a third straight day Monday but reported little improvement.

"We're probably considering slowing him down," Gibson said. "I don't want to push him early. We're looking for the longevity of when he gets going that he keeps going."

Arroyo, 37, has never been on the disabled list or missed a turn in the rotation, making at least 30 starts in each of the past nine seasons.

He signed a two-year contract with the D-backs on Feb. 7.

"Our thought process is, let's keep the pressure off him," Gibson said. "He's felt bad before and not been on the DL, so we know his make-up and his personality. He'd do almost anything to avoid that. That's not really how we want him to approach it at this point in the season. If it was September, maybe, but it's early in the season. Again, we want to get him right and get him throwing for the remainder and the duration."

The Diamondbacks do have options should Arroyo not be available. Randall Delgado and Josh Collmenter have starting experience, though Collmenter has not been stretched out. Then there is Archie Bradley, who has not allowed a run in 6.1 innings this spring.